Journal of Environmental Protection, 2016, 7, 1561-1570 http://www.scirp.org/journal/jep

ISSN Online: 2152-2219 ISSN Print: 2152-2197

DOI: 10.4236/jep.2016.711129 October 27, 2016

Assessment of Organic Compounds as Vehicular Emission Tracers in the Aburrá Valley Region of Colombia

Enrique Posada1, Miryam Gómez2, Viviana Monsalve1

1INDISA, Group of Process, Energy and Environmental Studies, Medellín, Colombia 2Politécnico Colombiano Jaime Isaza Cadavid, Group GHYGAM, Medellín, Colombia

Abstract The Aburrá Valley region in Colombia, with Medellín as its main city, is an urban centre with about three million people. An investigation was carried out to deter-mine a set of baseline concentrations for VOC compounds associated with diesel fuel and gasoline, as vehicular emission tracers in the region. The VOC measurement campaigns, based on TENAX tube sampling and analysis according to TO-17 EPA method, were done in areas of low and high vehicular flow as well as on-board mea-surements covering major Medellín road networks during 24 hours. The results showed that there was a relation between VOCs concentrations and vehicular activi-ty. The diesel fuel sulfur content was also found as an important factor on VOC hy-drocarbon formation.

Keywords VOCs, Vehicular Pollution Tracers, Vehicular Emissions, Urban Pollution, Rural Pollution

1. Introduction

VOCs tend to be polluting considering both their inhalation and contact effects and as a source of secondary pollutants. For the present study, they were classified into two (2) groups: poly-nuclear aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons (AH). Table 1 shows the list of VOCs studied and some basic characteristics.

The studied VOCs behave differently, following the two main types (alkanes [AH], and PAH) and this has to do with their molecular weight, as shown in the behavior of their vapor pressure and boiling point, properties that have to do with their presence in the atmosphere (Figure 1 and Figure 2).

How to cite this paper: Posada, E., Gómez, M. and Monsalve, V. (2016) As-sessment of Organic Compounds as Vehi-cular Emission Tracers in the Aburrá Val-ley Region of Colombia. Journal of Envi-ronmental Protection, 7, 1561-1570. http://dx.doi.org/10.4236/jep.2016.711129 Received: August 16, 2016 Accepted: October 24, 2016 Published: October 27, 2016 Copyright © 2016 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/

Open Access

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Figure 1. VOCs studied and their vapour pressures as related to molecular weight.

Figure 2. VOCs studied and their boiling points as related to molecular weight. Table 1. VOCs studied

Compound Molecular

weight Vapor pressure at

25˚C, mm Hg

Boiling temperature

at atm. pressure, ˚C Nature Formula

n-Nonane 128.3 4.45 150.6 AH C9H20

n-Decane 142.3 1.43 174.2 AH C10H22

n-Undecane 156.3 0.412 196.0 AH C11H24

n-Dodecane 170.4 0.135 214.0 AH C12H26

n-Tridecane 184.4 0.0560 232.0 AH C13H28

n-Tetradecane 198.4 0.0116 253.0 AH C14H30

n-Pentadecane 212.4 0.00310 268.0 AH C15H32

Naphthalene 128.2 0.0850 218.0 PAH C10H8

1-Methylnaphthalene 142.2 0.0670 240.0 PAH C11H10

2-Methylnaphthalene 142.2 0.0550 241.0 PAH C11H10

Phenanthrene 178.2 0.000121 332.0 PAH C14H10

1-Methylphenanthrene 192.3 0.0000501 354.0 PAH C15H12

2-Methylanthracene 192.3 0.0000727 353.5 PAH C15H12

0

50

100

150

200

250

300

350

400

120 140 160 180 200 220Boi

ling

tmpe

ratu

re a

t atm

osph

eric

pr

essu

re, °

C

Molecular weightAlkanes PAH

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A review [1] [2] of the health impact and occupational limits of the studied VOCs is shown in Table 2.

In general, VOCs play an important role in environmental problems by their accu-mulation and persistence in the environment [3]. Some VOCs, especially those of high molecular weight, resist oxidation processes and become persistent, being adsorbed on particles and transported over long distances [4], powering the global greenhouse ef-fect.

So far no studies of these compounds have been done locally, so it is deemed impor-tant to carry out an exploratory work, in parallel with the fact that sulphur content of diesel fuel is undergoing changes at the time, from 2000 to 50 ppm and it is desired to correlate those changes with the said VOCs concentrations.

Alkanes tend to be emitted by vehicles, as they are components of fuels. Table 3 shows typical contents of studied VOCs in low sulfur diesel and gasoline [5]. The other studied PAHs come from oil and coal tars and incomplete combustion, including wood combustion; Phenanthrene is also associated with cigarette and marihuana smoke and charcoal broil. Table 2. Occupational data for some of the VOCs studied. studied

Compound Residence half time in air, hr

Health impact Occupational limits

n-Nonane 40.8

Irritation eyes, skin, nose, throat; headache, drowsiness, dizziness, confusion, nausea,

tremor, discordination

TLV: 200 ppm (1050 mg/m3)

n-Decane 33.2 Irritation eyes, skin.

Little impact TLV Not established

n-Undecane 29 No clear indication of risks TLV Not established

n-Dodecane 27 Irritation eyes,

skin. Little impact

TEEL-0: Concentration below which people will experience

no adverse health effects is 0.015 ppm (105 μg/m3)

n-Tridecane 24

Irritating to eyes and skin. Inhalation causes irritation

of the lungs and respiratory system.

TLV Not established

n-Tetradecane 19.2 Irritation eyes, skin. Inhalation

causes irritation of the lungs and respiratory system

TLV Not established

n-Pentadecane 17 No clear indication of risks TLV Not established

Naphthalene 18 Irritating to skin and eyes TWA 10 ppm (50 mg/m3)

1-Methylnaphthalene 7.3 Irritation. Toxic by all routes

(i.e., ingestion, inhalation, and skin contact)

TLV = 0.5 ppm (2.9 mg/m3)

2-Methylnaphthalene 7.4 Irritating to skin TLV = 0.5 ppm (2.9 mg/m3)

Phenanthrene 36 - 1570

A known irritant, photosensitizing skin

to light. Potential occupational carcinogen

TWA = 0.028 ppm (0.2 mg/m3)

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Table 3. Typical contents of studied VOC in low sulfur diesel and gasoline

Compound Type % in typical diesel low S fuel % in gasoline

n-Nonane AH 0.84 0.24

n-Decane AH 0.92 0.19

n-Undecane AH 0.93 0.15

n-Dodecane AH 1.01 0.11

n-Tridecane AH 1.61 0.09

n-Tetradecane AH 1.21 0.03

n-Pentadecane AH 1.09 0.01

Total studied AH AH 7.61 0.82

Naphthalene PAH 0.36 0.30

2. Materials and Methods

The apparatus set up for the sampling is described in Figure 3. The sampling method applied was EPA TO-17 using 90 mm length, 5 mm diameter

stainless steel TENAX adsorption tubes filled with appropriate sorbent materials, pre-pared and supplied by the DRI (Desert Research Institute at Reno, Nevada, USA). The chemical analysis of the studied VOCs was also done at the DRI, using the Agilent Thermal Desorption-Gas Chromatograph/Mass Spectrometer (TD-GC/MS) system.

The environmental samples were taken in a measurement campaign conducted in three sites, two of them with heavy traffic, the other one with low or inexistent traffic, from July to August 2011, with sampling periods of 24 hours. Each zone was evaluated during a week.

Additional samples were taken in the discharge of a diesel motor working under standardized laboratory conditions with diesel fuel of variable sulfur content. Run cycles followed standard ECE-M2 at 2420 rpm. Figure 4 shows a scheme for the run cycle.

3. Methodology and Results 3.1. Urban and Rural Sites

The VOC measurement campaign was conducted in three sites, two of them with heavy traffic (Poblado zone and Botanical Garden Park), the other one with low or inexistent traffic (Arví Park), from July to August 2010, with sampling periods of 24 hours. Each zone was evaluated during a week. Another sample was taken sampling during 24 hours continuously within a vehicle moving through designed zones in the city (On Board test). In the Figure 5, the sampling sites are located in the Aburrá Valley map. Table 4 shows the concentrations in the urban and rural zones, and in the on-board 24 hour samples. It is clear that rural areas have lower VOCs concentrations than urban ones.

Figure 6 compares the VOC concentrations found for the zones. It was found that the higher concentrations of the studied tracers correspond to pentadecane and naph-

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Figure 3. Description apparatus for VOC measurement (left) and apparatus located in the sam-pling zone (right). Table 4. Concentrations in urban and rural zones, and in the on-board 24-hour samples studied.

Compound Poblado 05/08/10

Poblado 07/08/10

Poblado 10/08/10

Botanic Garden 20/08/10

Arvi Park 31/08/10

On-Board 02/09/10

Type of zone urban urban urban urban rural urban

n-Nonane 0.870 0.736 0.769 1.896 0.060 1.919

n-Decane 0.980 0.696 0.693 2.273 0.046 1.986

n-Undecane 0.668 0.473 0.467 1.417 0.038 1.728

n-Dodecane 0.389 0.301 0.324 0.685 0.025 0.564

n-Tridecane 0.274 0.237 0.237 0.516 0.031 0.730

n-Tetradecane 0.244 0.218 0.225 0.583 0.027 1.588

n-Pentadecane 0.241 0.190 0.207 0.986 0.057 6.379

Naphthalene 0.989 0.839 0.836 2.269 0.139 0.637

1-Methylnaphthalene 0.212 0.179 0.200 0.741 0.010 0.322

2-Methylnaphthalene 0.428 0.357 0.407 1.520 0.016 0.576

Phenanthrene 0.038 0.023 0.022 0.141 0.005 1.279

1-Metylphenanthrene 0.000 0.000 0.000 0.158 0.000 0.426

2-Methylanthracene 0.000 0.000 0.000 0.182 0.000 0.523

Total studied VOC 5.334 4.248 4.388 13.369 0.456 18.657

Total studied AH 3.666 2.851 2.922 8.357 0.286 14.894

Total estudied PAH 1.667 1.398 1.466 5.012 0.170 3.763

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Figure 4. Run cycle scheme.

Figure 5. Sampling sites (Google map image 2016). thalene. The on-board sample shows higher VOC’s concentrations than the other sam-pling sites. Probably because the on board test environment was in continuous contact with mobile sources. Figure 7 shows comparative result for all the zones in terms of total VOCs.

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Figure 6. Comparative results for VOC concentrations in all studied zones.

Figure 7. Total VOC concentrations for the studied zones.

It is clear in Figure 7 that the concentrations of VOCs in urban areas are clearly greater than the ones in rural areas. Urban total VOCs were about 25 times greater than the rural area. All concentrations, as expected, are clearly much lower than the reported occupational limits for the substances shown in Table 2.

3.2. A Review of VOC Concentrations in Urban and Rural Areas around the World

Following results reported elsewhere [2] [6]-[9], Table 5 was prepared to compare val-ues reported around the world with the ones found in the present study, in order to have a comparative measure of the magnitude of the problem in the Medellín region.

This analysis shows, in general, local values lower than the typical ones reported around the world. The typical values shown were chosen by the authors after elimina-tion, at their own criteria, of extreme high values in the reported data.

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Table 5. VOC concentrations (range and typical) around the world and in this study.

Concentrations in urban areas (μg/m3) Concentrations in rural areas (μg/m3)

Compound Range around

the world

Typical around

the world

Average of this study

Range around

the world

Typical around

the world

Average of this study

n-Nonane 0.07 - 467 5.06 1.24 0.0 - 58.2 4.067 0.060

n-Decane 0.16 - 1100 18.68 1.33 0.0 - 161.2 5.919 0.046

n-Undecane 0.15- 59 7.66 0.95 0.018 - 0.54 0.279 0.038

n-Dodecane 0.0 -160 0.97 0.45 0.0 - 0.25 0.044 0.025

n-Tridecane 0.18-2.7 0.93 0.40 0.01-0.12 0.066 0.031

n-Tetradecane 0.0 - 36 8.46 0.57 0.0 - 0.116 0.058 0.027

n-Pentadecane 0.19 - 158 15.47 1.60 0.01 -0.149 0.080 0.057

Naphthalene 0.0 - 77 2.27 1.11 - - 0.139

1-Methylnaphthalene 0.00 - 5.1 0.59 0.33 - - 0.010

2-Methylnaphthalene 0.00 - 1.1 0.39 0.66 - - 0.016

Phenanthrene 0.01 - 129 1.08 0.30 0.0 -0.032 0.006 0.005

Total 61.58 8.94 10.52 0.456

3.3. Diesel Engine Exhaust Concentrations

At the time of the study, S content of diesel fuel used in the region was undergoing changes, from 2000 ppm to 50 ppm and it was desired to correlate those changes with VOCs concentrations in the exhaust gases coming from a diesel motor working under standardized laboratory conditions.

Table 6 shows the results, which show a clear effect of the sulfur content of the fuel on the emissions of the studied VOCs.

4. Conclusions

The region atmosphere shows presence of VOCs. The concentrations in urban areas are clearly greater than the ones in rural area. In

the average urban total VOCs are 27 times larger. The values found in rural and urban areas tend to be smaller than the typical values

reported, around the world, in the literature. Total VOCs show values around 15% of the reported typical values for urban areas and about 5% for rural areas.

The VOC concentrations are related to vehicle emissions, especially to diesel fuel vehicle emissions.

An initial baseline has been established which should be useful for future work and public policy in relationship to vehicle related pollution control.

Reducing S content on diesel fuel has been a beneficial step in this direction.

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Table 6. VOC concentrations in diesel fuel motor exhaust and sulfur content in diesel fuel.

Compound Fuel with sulfur

at 50 ppm, µg/m3 Fuel with sulfur

at 500 ppm, µg/m3 Fuel with sulfur

at 2100 ppm, µg/m3

n-Nonane 177 62 160

n-Decane 407 153 528

n-Undecane 254 203 501

n-Dodecane 199 250 649

n-Tridecane 186 311 586

n-Tetradecane 111 311 450

n-Pentadecane 61 361 356

Naphthalene 179 140 141

1-Metylnaphthalene 87 134 176

2-Metylnaphthalene 170 218 317

Phenanthrene 1.43 12.83 5.60

Total studied VOC 1832 2155 3869

Total studied AH 1395 1650 3230

Total estudied PAH 437 505 639

Acknowledgements

This work was supported by POLITÉCNICO COLOMBIANO JAIME ISAZA CADAVID and ECOPETROL. We acknowledge the DRI Institute for the analytical and sampling assistance and the University of Antioquia, GIMEL group, for the work done in the laboratory motor testing.

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